1. Field of the Invention
The present invention relates to a unit swing type power unit, in which a transmission casing accommodating therein a continuously variable transmission mechanism and an engine body are joined integrally, and a saddle-ride type vehicle provided with the power unit.
2. Description of Related Art
Scooter type motorcycles generally have mounted thereon a unit swing type power unit, in which an engine body and a transmission casing accommodating therein a continuously variable transmission mechanism are joined integrally.
In some cases, this kind of power unit comprises a winding diameter controlling mechanism, in which an electric motor is used to variably control a belt wound diameter of a primary sheave on the basis of engine speed, vehicle speed, etc. so as to obtain an optimum transmission gear ratio corresponding to an operating state of an engine (see, for example, Patent Application No. 02-340927)
The conventional power unit described above involves a problem that a vertical dimension of an engine body becomes large depending upon an arrangement and a construction of a drive member, which varies a wound diameter of a primary sheave, and an electric motor, which drives the drive member.
Also, this conventional kind of power unit needs improvement in fuel consumption through reduction in loss horsepower.